Fuel rails for supplying fuel to fuel injectors of internal combustion engines are well known. A fuel rail is essentially an elongate fuel manifold connected at an inlet end to a fuel supply system and having one or more ports for mating with one or more fuel injectors to be supplied.
Fuel rail systems may be recirculating, as is commonly employed in diesel engines. Fuel rail systems are more typically “returnless” or dead ended, wherein all fuel supplied to the fuel rail is dispensed by the fuel injectors.
A well-known problem in fuel rail systems, and especially in returnless systems, is pressure pulsations in the fuel itself. Therefore, damping devices are useful for controlling fuel system acoustical noise and for improving cylinder-to-cylinder fuel distribution. Various approaches for damping pulsations in fuel delivery systems are known in the prior art.
For a first example, one or more spring diaphragm devices may be attached to the fuel rail or fuel supply line. These provide only point damping and can lose function at low temperatures. They add hardware cost to an engine, complicate the layout of the fuel rail or fuel line, can allow permeation of fuel vapor, and in many cases simply do not provide adequate damping.
For a second example, the fuel rail itself may be configured to have one or more relatively large, thin, flat sidewalls which can flex in response to sharp pressure fluctuations in the supply system, thus damping pressure excursions by absorption. This configuration can provide excellent damping over a limited range of pressure fluctuations but it is not readily enlarged to meet more stringent requirements for pulse suppression. Further, the thin sidewall can be accessible to accidental puncture.
For a third example, a fuel rail may be configured to accept an internal damper comprising a sealed pillow, or metal bladder, typically having a flat oval cross-section and formed of thin stainless steel. Air or an inert gas is trapped within the pillow. The wall material is hermetically sealed and impervious to gasoline. Such devices have relatively large, flat or nearly-flat sides that can flex in response to rapid pressure fluctuations in the fuel system. Internal dampers have excellent damping properties, being easily formed to have diaphragm-like walls on both flat sides, and can be used in rails formed of any material provided the rail is large enough to accommodate the damper within. An internal damper may be advantageous over the wall-formed damper, in that mechanical failure of the damper results only in flooding of the damper itself.
In simplest form, a prior art damper is produced by simply crimping together the ends of a flat oval steel or stainless steel tube to form a flat section. A hermetic seal is created by welding the resulting seam. The crimping process causes the sides to widen out in a gradual manor from the flat-oval section to the flattened area. This results in an adequate end sealing method that will withstand pressure cycling for small dampers. However, this type of end form is inadequate for applications wherein larger dampers are required. The cyclic motion of the damping surfaces transfers the motion along the transition and can fatigue the material where it is bent over on itself. In this area, the material is stressed by the crimping operation. One solution is to fold the sides inward prior to flattening, forming thereby a “milk carton” type closure, as disclosed in commonly owned U.S. Pat. No. 6,655,354, which stiffens the ends and isolates from motion the areas wherein the material is bent over onto itself. This approach adds cost to the manufacturing process.
What is needed in the art is an improved method of sealing the end of a pulse damper to produce a seal that can withstand working pressure cycles over the expected working lifetime of a pulsation damper.
It is a principal object of the present invention to extend the working life of a pulsation damper in a liquid medium.